I have just got the aircon working in my daughter's 1989 405. But, I note that if the A/C switch is depressed, when the ignition is switched to the accessory postion, the compressor clutch is energised. This seems wrong.
Unfortunately, the A/C system isn't covered at all in the Haynes manual no.
1559 that I have (petrol 1989-97).I'd appreciate it if someone else with this model 405 could tell me if their car also activates the compressor clutch as above
All the best
Ron